The present invention relates generally to the field of cutting and relates more particularly to an apparatus for cutting sheet materials such as limp fabrics, plastics, paper and similar products by means of high velocity fluid cutting jets.
The use of a high velocity fluid cutting jet for cutting materials such as fabrics, wood and other products has been known for some time. The cutting jet is usually produced by forcing water in a continuous stream through a nozzle at very high pressures ranging between 10,000 psi and 100,000 psi. The jet is oriented with its axis generally perpendicular to the surface of the material to be cut, and the cutting operation is effected by the jet as the nozzle is moved relative to the material surface. The energy associated with the jet of fluid, which exits the nozzle between 1,000 and 3,000 fps, may only be partially dissipated by the material in the path of the jet stream. Some means is generally needed, therefore, to dissipate the unused energy of the fluid stream after the jet passes through the material.
A fluid jet receiver capable of dissipating the energy of the jet in a cutting machine is described in U.S. Pat. No. 4,137,804, having the same assignee as the present invention. In this referenced patent, the receiver is in the form of a vortex chamber positioned on the side of the material opposite the fluid jet nozzle with the inlet of the receiver opening toward the nozzle. The carriage which supports the nozzle also supports the receiver to assure that the inlet of the receiver is in constant alignment with the axis of the fluid jet as the jet exits the nozzle while the nozzle moves relative to the sheet material.
As the cutting jet is dissipated over the thickness of the material, the jet experiences a high rate of deceleration. As a result of the high rate of deceleration, the point at which the jet exits the material may lag considerably behind the point at which the jet enters the material while the jet is moved relative to the sheet material. This lag may cause the receiver, whose inlet remains in alignment with the nozzle, to fail to catch the exiting jet stream. Of course this problem could be substantially eliminated by moving the nozzle at a slow rate of speed relative to the material, but this solution may substantially increase the amount of time, and therefore the cost, necessary to perform a cutting operation. The problem may also be eliminated by providing a receiver whose inlet is large relative to the size, or cross section, of the cutting jet, but this solution increases the likelihood that jet backsplatter resulting from the jet striking against the interior of the receiver will disperse the jet fluid against the material, and in the cutting apparatuses that require the receiver to provide partial support for the material, a relatively large receiver inlet would allow the material to sag or droop into the inlet and thereby promote the misalignment of the cutting jet and the desired cutting path in the bottom layers of the material.
It is, accordingly, a general object of the present invention to provide a sheet material cutting apparatus utilizing a fluid jet and a fluid jet receiver which circumvent the aforementioned problem associated with fluid jet lag with no reduction in speed of the nozzle relative to the material nor increase in size of the receiver inlet.